content: /*
   * Copyright 2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package hu.akarnokd.agera;
  
  import android.support.annotation.NonNull;
  
  import java.util.Queue;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Makes sure tasks offered are executed in a FIFO order on an Executor.
   */
  public final class Trampoline
          extends AtomicInteger
          implements Runnable {
  
      final Queue<Runnable> queue;
  
      final Executor executor;
  
      public Trampoline(@NonNull Queue<Runnable> queue, @NonNull Executor executor) {
          this.queue = queue;
          this.executor = executor;
      }
  
      @Override
      public void run() {
          do {
  
              queue.poll().run();
  
          } while (decrementAndGet() != 0);
      }
  
      public void offer(@NonNull Runnable task) {
          queue.offer(task);
  
          if (getAndIncrement() == 0) {
              executor.execute(this);
          }
      }
  }
  